Core B provides support for the use by Program Project scientists of neutron scattering instruments at the NIST Center for Neutron Research (NCNR) in Gaithersburg, Maryland. The success of the Program Project, entitled Making Sense of Voltage Sensors, depends almost entirely on the use of neutron diffraction and reflectivity measurements to determine the disposition of potassium channels and their voltage sensors in lipid bilayer membranes. The specific aim of Core B is to provide technical and training support at the NCNR for Program scientists using neutron scattering instruments, particularly the Advanced Neutron Diffractometer/Reflectometer (AND/R). Technical and training support will be provided by Dr. David Worcester, who is one of the early pioneers of membrane neutron diffraction. Serving as the senior neutron scientist, he will be stationed full-time at the NCNR to work closely with Project scientists to help them plan, execute, and analyze neutron scattering experiments. He will report to and work closely with the Program Director to assure the timely planning and execution of the neutron scattering work proposed in Projects 2 and 3.